While many consumers may be kicking landlines to the curb in favor of cell phones, most growing businesses are behaving more circumspectly. "We've found it's not so much a trend of [businesses] moving entirely away from the landline as it is shifting a lot of minutes over to wireless," says Matthew DelPercio, associate analyst with research organization The Yankee Group.

Looking past mobile phones, VoIP over Wi-Fi could help move the sluggish landline exodus along. Dual-mode handsets that seamlessly connect to Wi-Fi at the office and to cellular on the go are especially intriguing. But Yankee Group analyst Gary Chen sees challenges to the young technology in the forms of a lack of industry standards, reduced battery life and quality of service issues. Chen recommends that businesses invest in VoIP over Wi-Fi at this point only if there's a clear need for it, your network can handle the added traffic and you can live with its current shortcomings.

"I don't think landlines will ever be completely displaced," says DelPercio. "I don't see VoIP as a big revolution, but as an evolution."

Dependence on cell phones may be an early sign of a shift away from landlines, but entrepreneurs still demand landlines' reliability and quality. They can't afford dropped calls or poor voice quality during business conversations. Still, the cost savings and benefits of VoIP will bring in an increasing number of businesses. "Landline displacement is inevitable," says DelPercio. "It's just not going to be as extreme as people think."